Animal Care

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TREATING INFLAMMATION

Mark Newton-Clarke MAVetMB PhD MRCVS, Newton Clarke Veterinary Surgeons

With summer hopefully well on the way, many of us are spending more time being active, either in the garden, walking or doing more strenuous exercise. This is all good for our mental and physical well-being and I’m sure our pets enjoy the benefits of happier owners. As Tracey and I discovered last week, there is a downside to a sudden increase in exertion, when muscular effort one day resulted in significant pain the next (speak for yourself, I hear my wife say!). We walked 20 miles of the Pembrokeshire coast path in 6 hours, a good pace by my standards and even Portia the black Labrador was snoozing by 8pm. She could have had the decency to look a little bit stiff the next day.

The reason I mention this is to follow on from last month when I discussed pain and its control. One of the commonest sources of pain is inflammation and for this reason, we use anti-inflammatory medicines to help control it. Acute inflammation is the body’s response to injury and disease and it makes us feel painful and ill, so clinicians obviously have a vested interest in treating it, not forgetting the underlying cause. The mechanism of inflammation is complex and involves chemicals that are released from damaged tissue that in turn stimulate pain receptors and increase blood flow to the affected area. It’s not difficult to imagine why this response has evolved, as the pain discourages further use of the injured part while the increased blood flow starts the healing process but also causes local heat and swelling.

This system works well for relatively minor, acute trauma that affects an isolated part of the body’s tissues and for systemic diseases that are self-limiting, for example, a viral infection. The problems start when the inflammation becomes chronic (i.e. long-standing) or affects an organ trapped inside a rigid container, like the brain and spinal cord. Swelling inside the cranium is

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very serious as the brain is compressed, which it really does not like. Depending on the location and severity of the swelling, symptoms can range from personality and behavioural changes to seizures, coma and acute death. Although much more common in human medicine, we do encounter increased intracranial pressure in dogs and cats, often as a result of trauma or as a congenital defect (hydrocephalus and breedspecific cranial deformities). There is another organ that cannot tolerate inflammation and it’s been a topic of conversation over the last couple of years; the lung. Just a tiny amount of extra fluid in the lung prevents the exchange of oxygen with carbon dioxide and this is how certain viral infections can be fatal (don’t we all know). It’s not the virus per se that’s the problem, it’s the body’s response. Non-steroidal antiinflammatories are not powerful enough for serious cases of lung inflammation which is why the use of a potent steroid, dexamethasone, is considered.

I mentioned the complexity of inflammation and through the clever techniques developed by molecular biochemists, we now know the sequence of events. Pivotal to the inflammatory response is a group of fatty molecules called ‘prostaglandins’ (PGs). Named after an exclusively male genital gland (guess which one!) this diverse group of hormones orchestrates inflammatory responses. Non-steroidal anti-inflammatories (nsaids) like meloxicam (widely used in human and veterinary medicine) reduce the production of PGs and so reduce inflammation and hence pain. But it’s never that easy. Some PGs are really helpful, maintaining blood flow to many parts of the body, e.g. gut, kidney and many other tissues, and these helpful PGs are affected by nsaids along with the pain-producing PGs. That’s why long-term nsaid use comes with a risk i.e. ulceration of stomach or intestine and reduction in kidney function. Having said that, these medicines are used safely millions of times a day in both humans and animals and can provide significant pain relief without any problems.

Most of the above applies to acute inflammation but like pain, inflammation can become chronic. The healing process becomes long-standing in an attempt to finish the job but the destructive element of the inflammatory process prevents this. What results depends on the part of the body affected but many of us are familiar with the effects of chronic joint inflammation. Here, joint surfaces are damaged, scar tissue causes permanent thickening and new bone is formed around the joint (osteoarthritis). This is an area where inflammation meets degeneration, a very unfortunate part of getting older for us and our pets. The point is, chronic inflammation makes the degenerative effects of ageing worse and clinicians should not lose sight of this. So no matter how old your dog or cat is, treating inflammation can be beneficial, not just to reduce pain but also to slow down the effects of the advancing years.

It is with sadness that I report the passing of BJ, our Swan House cat. About a year ago, I wrote about his battle with inflammatory bowel disease that in cats, often affects other essential organs. The steroids we used as treatment finally stopped having their beneficial effects that maintained his quality of life and so, surrounded by the people he liked best, BJ was gently sent on his way. We will all miss him but it was a life lived and his memory will live on.

WHAT IS IBR?

Jenny Gibson MRCVS, The Kingston Veterinary Group

IBR (infectious bovine rhinotracheitis) is a viral infection caused by bovine herpes virus type 1 (BHV-1). It is a highly contagious disease, that can affect cattle of all ages. It commonly affects the respiratory and reproductive systems. The virus spreads through respiratory secretions and infection occurs via inhalation from close contact of infected animals. IBR can also be spread by semen of infected bulls, often resulting in abortions and foetal deformities. Once they recover from the initial infection, they then develop a latent infection. This means they will always have the virus, however, the virus will lay dormant for the majority of the time but when the animal is under stress, the virus will start multiplying and cause disease again.

In adult cows, infection is associated with a drop in milk yield for a prolonged period of time, reduced fertility and abortions. Very occasionally they may show signs of a cough and ocular discharge and on occasion, the disease may be so mild that it may be overlooked.

Calves often have more obvious and severe signs. The virus causes inflammation of the upper respiratory tract and the end result is often pneumonia. Mild cases present with a cough and conjunctivitis, whereas in more severe cases they may have a fever, depression, inappetence, difficulty breathing and a purulent ocular and nasal discharge. In younger cattle, if treatment is not sought quickly, this virus can then lead to other secondary bacterial and viral infections.

During an outbreak of IBR, the morbidity rate may be as high as 100%, but the mortality rate is generally very low at approximately 2%. It is most often the first few cows to develop the disease that show the most

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severe symptoms. Stressful events such as calving, transportation and housing often trigger activation of the virus. Clinical signs usually become apparent 2-3 weeks following the stressor.

There are two ways in which a diagnosis of IBR in an individual cow can be performed; the first is from a blood sample which can detect latent/pre-exposed infection. The other method of diagnosis is via nasal swabs (similar to the Covid-19 swabs that we perform) which directly detects the virus in active infections. The level of IBR within a herd can be determined through measuring bulk milk antibody titres.

As IBR is a virus, unfortunately, there is no specific treatment. Those with a fever would benefit from antiinflammatories and any animal demonstrating signs of secondary bacterial infection may be dosed with antibiotics. Nutritional support may be required for calves or those individuals going through a period of inappetence. Isolation of infected animals and vaccines may be used in an outbreak to protect others.

Prevention of IBR infection is mainly achieved via vaccination, however, it does not stop already infected animals from shedding the virus at a later date. The vaccines commonly cover other respiratory diseases at the same time and either come as an intramuscular injection or intranasal vaccines for calves. The timing of vaccination is important to allow full protection. Further to vaccination, IBR can be prevented from entering the herd through careful biosecurity measures and strict quarantine of purchased stock.